Gregg and Smulders, who play S.H.I.E.L.D. agents Coulson and Hill, talk to THR about creating characters who were faithful to the mythology of Marvel universe -- with or without a precedent in film's source material.

As much as it’s the culmination of Marvel’s various origin stories and individual adventures for Iron Man, Thor and Captain America, The Avengers is an epic adaptation of Marvel Comics’ superhero crossover series of the same name. But not all of the characters in the film first originated on the pages of the comic book – or any comic book, for that matter: Agent Phil Coulson, played by Clark Gregg, first turned up in the first Iron Man film, and has since become a staple of Marvel’s cinematic universe.

Despite the freedom that Gregg enjoyed in creating Agent Coulson, the actor told The Hollywood Reporter that he feels like all of the Marvel movies make a concerted effort to be respectful of their printed-page source material.

“The fanboys and girls are very interested in [mythology] like, ‘that goes directly against what goes in the comic’,” Gregg said. “And they can’t do that with me. I feel like these movies are designed to respect those comics, so I always made a point of checking out what there was about S.H.I.E.L.D.”

Nevertheless, Gregg indicated that he relied upon Marvel for background information about Coulson’s employers, even if he created the character exclusively via the script. “The great thing is that the Marvel guys are there and you say, ‘I need a little more background on Nick Fury and S.H.I.E.L.D.,’ and the next day they hand you this thing that any fanboy would die for, kind of an encyclopedia illustrated about the history of S.H.I.E.L.D.”

The Avengers marked Gregg’s co-star Cobie Smulders’ first foray into the Marvel movies, playing Agent Maria Hill, who did not exist in the comic books, either. But Smulders said that she relied upon writer-director Joss Whedon to sort of bridge the gap between adapting an iconic character and simply creating a believable one on screen.

“Joss Whedon, he is really hands-on and he wants every character to have a life on and off screen,” Smulders said. “He is really involved in making sure that every person has their moments. And I really felt like a part of a team – I really felt linked to Coulson and to Fury and especially our role in the film.

“We were constantly overseeing everything,” she continued. “We were actually watching, so we always had to be aware at all times.”